This invention relates to the field of high pressure processing. More particularly, this invention relates to the field of high pressure processing of a semiconductor wafer.
Processing of semiconductor wafers presents unique problems not associated with processing of other workpieces. Typically, the semiconductor processing begins with a silicon wafer. The semiconductor processing starts with doping of the silicon wafer to produce transistors. Next, the semiconductor processing continues with deposition of metal and dielectric layers interspersed with etching of lines and vias to produce transistor contacts and interconnect structures. Ultimately in the semiconductor processing, the transistors, the transistor contacts, and the interconnects form integrated circuits.
A critical processing requirement for the processing of the semiconductor wafer is cleanliness. Much of semiconductor processing takes place in vacuum, which is an inherently clean environment. Other semiconductor processing takes place in a wet process at atmospheric pressure, which because of a rinsing nature of the wet process is an inherently clean process. For example, removal of photoresist and photoresist residue subsequent to etching of the lines and the vias uses plasma ashing, a vacuum process, followed by stripping in a stripper bath, a wet process.
Other critical processing requirements for the processing of the semiconductor wafers include throughput and reliability. Production processing of the semiconductor wafers takes place in a semiconductor fabrication facility. The semiconductor fabrication facility requires a large capital outlay for processing equipment, for the facility itself, and for a staff to run it. In order to recoup these expenses and generate a sufficient income from the facility, the processing equipment requires a throughput of a sufficient number of the wafers in a period of time. The processing equipment must also promote a reliable process in order to ensure continued revenue from the facility.
Until recently, the plasma ashing and the stripper bath were found sufficient for the removal of the photoresist and the photoresist residue in the semiconductor processing. However, recent advancements for the integrated circuits have made the plasma ashing and the stripper bath untenable for highly advanced integrated circuits. These recent advancements include small critical dimensions for etch features and low dielectric constant materials for insulators. The small critical dimensions for the etch features result in insufficient structure for lines to withstand the stripper bath leading to a need for a replacement for the stripper bath. Many of the low dielectric constant materials cannot withstand an oxygen environment of the plasma ashing leading to a need for a replacement for the plasma ashing.
Recently, interest has developed in replacing the plasma ashing and the stripper bath for the removal of the photoresist and the photoresist residue with a supercritical process. However, high pressure processing chambers of existing supercritical processing systems are not appropriate to meet the unique needs of the semiconductor processing. In particular, high pressure chambers of existing supercritical processing systems do not provide a mechanism for handling the semiconductor wafer during loading and unloading nor for holding the semiconductor during e supercritical processing. It is critical that the mechanism provides handling and holding of the semiconductor wafers without breaking or otherwise damaging the semiconductor wafers.
What is needed is a mechanism for handling semiconductor wafers during loading and unloading of the semiconductor wafers into and out of a supercritical processing chamber and for holding the semiconductor wafers during the supercritical processing which promotes cleanliness, which is economical, which is efficient, and which does not break the semiconductor wafers.
The present invention is a vacuum chuck for holding a semiconductor wafer during high pressure processing. The vacuum chuck comprises a wafer platen, first through third lift pins, and an actuator mechanism. The wafer platen comprises a smooth surface, first through third lift pin holes, and a vacuum opening. In use, the vacuum opening applies vacuum to a surface of a semiconductor wafer, which chucks the semiconductor wafer to the wafer platen. The first through third lift pins mount within the first through third lift pin holes, respectively. The actuator mechanism couples the first through third lifting pins to the wafer platen. The actuator mechanism operates to extend the first through third lift pins in unison above the smooth surface of the wafer platen. The actuator mechanism operates to retract the first through third lift pins in unison to at least flush with the smooth surface of the wafer platen.